Surgical Cutting Device

ABSTRACT

A surgical knife has been developed. The knife includes a blade with an edge that contacts tissue of a patient and a differential amplifier circuit that provides a signal of voltage and current to the blade at a certain frequency and waveform. The device also includes an output monitor feedback circuit that monitors frequency and amplitude data from the differential amplifier circuit and a return monitor feedback circuit that monitors that monitors frequency and amplitude data from the tissue of the patient. The device has a microprocessor that receives the frequency and amplitude data from the output monitor and the return monitor and adjust the voltage, frequency and waveform provided by the differential amplifier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 61/933,611 titled “Cordless Surgical Cutting Device”that was filed on Jan. 30, 2014.

FIELD OF THE INVENTION

The invention relates generally to medical devices. More specifically,the present invention relates to a surgical cutting device.

BACKGROUND

Electronic surgical instruments are well known have been used forcutting and coagulating tissue in a surgical environment since themid-twentieth century. A typical electronic instrument of this typeincludes a controller that is wired to the patient and also wired to thecutting tip of the instrument. However, the wire that connects thecontroller and the cutting tip limits freedom of movement by thesurgeon. Additionally, the wire may affect the precision and theposition of the incision. Finally, the wire may also be a source ofcontamination that will require additional sterilization procedures.Consequently, a need exists for an improved surgical cutting device.

SUMMARY OF THE INVENTION

One embodiment of the invention relates to a surgical apparatus,comprising: a blade with an edge for contacting tissue of a patient; adifferential amplifier circuit configured to provide a signal having avoltage and a current to the blade at a certain frequency and waveform;an output monitor feedback circuit that monitors frequency and amplitudedata from the differential amplifier circuit; a return monitor feedbackcircuit that monitors that monitors frequency and amplitude data fromthe tissue; and a microprocessor that receives the frequency andamplitude data from the output monitor and from the return monitor andadjusts at least one of the voltage, frequency and waveform provided bythe differential amplifier

Another embodiment of the invention relates to a surgical apparatus,comprising: a cordless surgical apparatus, comprising: a blade with asurface edge for contacting tissue of a patient, where the blade isoperably coupled to a receiving antenna; a signal amplifier with atransmitting antenna that transmits a signal to the receiving antenna ata certain frequency and waveform; an output monitor feedback circuitthat monitors frequency and amplitude data from a differential amplifiercircuit; a return monitor feedback circuit that monitors that monitorsfrequency and amplitude data from the tissue of the patient; and amicroprocessor that receives the frequency and amplitude data from theoutput monitor and from the return monitor and adjusts the voltage,frequency and waveform provided by the differential amplifier.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

It should be noted that identical features in different drawings areshown with the same reference numeral.

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a side view of the components in use of one embodiment of thepresent invention.

FIG. 3 is a schematic circuitry diagram of a passive tissue pad signalamplifier in use of one embodiment of the present invention.

FIG. 4 is a schematic circuitry diagram of an active tissue pad signalamplifier in use of one embodiment of the present invention.

FIG. 5 is a schematic circuitry diagram that shows details of the FIG. 1block diagram for one embodiment of the present invention.

FIG. 6 shows a diagram of electromagnetic coupling between the surgicalknife and the transmitting antenna that it attached to the tissue of thepatient for one embodiment of the present invention.

FIG. 7 shows an alternative embodiment of the invention that usesgravity to align the polarization of the receiving and transmittingantennas.

FIG. 8 shows which shows an alternative embodiment of the invention witha signal amplifier used for varying cutting frequencies.

DETAILED DESCRIPTION

A cordless surgical cutting device has been developed. One embodiment ofthe present invention operates as a surgical tool that cuts tissuewithout the use of a cord or wire. In this embodiment, the cuttingdevice is battery powered with a microprocessor that allows preciseadjustment of frequencies and pulse widths of the current of the device.The current loop of the device is completed using electrostatic couplingfrom the surface of the patient's skin, through the air, and back to anantennae/receiver in the hand-held cordless device.

During operation, the device applies power to the tip of a modularcutting surface or “blade” sufficient to non-thermally cauterize, cut,singe, or burn tissue. One component of the device is anantennae/receiver which facilitates a tuned circuit matched to the tipfrequency that provides electrostatic coupling to tissue, as shown inthe figures. Some embodiments of the present invention also have theability to monitor current with sufficient precision to to discernbetween different tissue types (based on the respective impedance) andto shut off current or warn a user if the blade is contacting anon-desired tissue type.

In addition, a conductive pad with a frequency matched to the tunedcircuit and antennae may be affixed to the patient to further enhancethe electrostatic coupling. The use of the tuned circuit, antenna orcopper pad, and conductive pad affixed to patient provides a return pathfor the knife current thus eliminating the need for wires which arerequired in existing surgical knife systems.

A preferred embodiment of the present invention, for use with surgery onhuman tissue, may operate with a current of 2-10 milliamps and a avoltage of 1000-3000 volts. During operation, the current may be loweredwhile the voltage is adjusted correspondingly to maintain a desiredpower level. The device may operate at a frequency of 400 kHz. In someembodiments, the device to operates across the RF spectrum to takeadvantage of increased efficiencies in size and power transfer. Forexample, the present device may adjust the operating frequency formaximum power transfer or for a specific type of tissue. However, thedevice when intened for use with surgery on a human is preferablyconfigured not to operate at lower frequencies in order to avoidpotentially interfering with cardiac functions of the patient. Theselower frequency ranges typically are between 16-100 Hz.

Referring now to FIG. 1 which shows a block diagram of one embodiment ofthe present invention. The cordless electronic surgical knife has aswitch 10 for a specific mode of operation and a switch 11 for anadditional specific mode operation. Other switches may include tocontrol additional modes of operation. Switch 10 and switch 11 areconnected to a microprocessor 12 that reads inputs from an outputmonitor feedback circuit 13 and a return monitor feedback circuit 15.The microprocessor 12 uses the inputs from the switches 10 and 11, theoutput monitor feedback circuit 13 and the return monitor feedbackcircuit 15 to generate a waveform that is sent to a waveform shapingcircuit 14 which drives the differential amplifier circuit 16. One legof the differential amplifier circuit 16 drives the cutting surface edge18 of the blade. A second leg of the differential amplifier circuit 16is connected to an electromagnetic pickup circuit 17 that provides anelectrostatic return path for the current generated by the cuttingsurface edge 18.

All of this circuitry may be battery powered. In a typical embodiment ofthe invention, a high current “10C” lithium polymer or “Lipo” typebattery may be used which will meet current demands of this embodimentof the invention. In other embodiments, battery technologies with highershort circuit current specifications may be used to achieve a batterysize of 2-5 cm². The weight and dimensions of the battery should beconsidered as a factor that potentially affects the mobility and ease ofuse of the device by the medical personnel.

The switches 10 and 11 are connected to the microprocessor 12 anddetermine the mode of operation. Modes of operation are not limited tobut may include cutting and coagulation. The microprocessor 12 generatesa waveform at a specific frequency, pulse width, periodicity and voltageappropriate to cut or coagulate specific tissue types based on feedbackreceived from the output monitor feedback circuit 13 and the returnmonitor feedback circuit 15. Further, the microprocessor 12 may vary thefrequency, the current, the pulse width, the periodicity, the waveformshape, and the output voltage to ensure and maintain operation of thedevice to optimally cut or coagulate tissue based on the feedbackreceived. The microprocessor 12 controls the waveform shaping circuit 14which performs additional shaping for the waveform and provides voltagelevel information which amplifies or attenuates the signal level that isfed to the input of the differential amplifier circuit 16.

The differential amplifier circuit 16 has a low impedance outputsufficient to provide the appropriate voltage and current to cut andcoagulate tissue. One leg of the differential amplifier circuit 16output is connected to the cutting surface edge 18 which is driven at avoltage, frequency, pulse width and periodicity or “duty cycle” (i.e.,the interval that a frequency is enabled or disabled) sufficient to cutor coagulate tissue. The electromagnetic pickup circuit 17 provides areturn path for the proper amount of current passing through the tissueand through the cutting surface edge 18 and is tuned to a resonantfrequency preferably matched to the frequency of the cutting surfaceedge 18.

The output monitor feedback circuit 13 provides zero-crossing data fortime analysis and amplitude data to the microprocessor 12. Inalternative embodiments of the invention, the output monitor feedbackcircuit 13 controls the waveform shaping circuit 14 directly. In otherembodiments, the feedback circuit may detect different tissue types andadjust voltage and current appropriately.

Referring now the FIG. 2 which shows is a side view of the components inuse of one embodiment of the present invention, the circuitry describedwith respect to FIG. 1 is housed within a surgical knife 22. The cuttingedge of the surgical knife 22 makes contact with tissue 21 when in use.The circuitry within the surgical knife 22 preferably drives the cuttingedge at a voltage, frequency, pulse width, periodicity and voltagesufficient to cut or coagulate the tissue 21 at the incision point 23.The current is electrostatically coupled to the surgical knife 22 andadditional electrostatic coupling, if required, is provided by a signalamplifier 24 that is affixed to the tissue 21.

The signal amplifier 24 makes electrical contact with the surface of thetissue and is connected to a tuned circuit that is resonant at thefrequency of the cutting surface edge 18. This provides a strongelectrostatic coupling with the electromagnetic pickup circuit 17providing a path for current to flow from the cutting surface edge 18through the tissue 21 and creating a cutting or coagulating action. Inother embodiments of the invention, the signal amplifier 24 increasesthe coupling with the electromagnetic pickup circuit 17. Referring backto FIG. 1, the electromagnetic pickup circuit 17 may include a pluralityof axes to improve electrostatic coupling while the instrument 22 ismoved in various positions relative to the surface of the tissue 21and/or the signal amplifier 24. FIG. 3 shows a schematic circuitrydiagram of a passive tissue pad signal amplifier for use in oneembodiment of the present invention. This amplifier includes a tunedcircuit 32 in contact with the tissue 31, preferably tuned to match thefrequency of the cutting edge 18. In an alternative embodiment, FIG. 4shows a schematic circuitry diagram of an active tissue pad signal. Thisamplifier includes two tuned circuits 42 and 44 and an amplifier 43 incontact with the tissue 41.

The construction of the invention as shown in FIG. 1 and FIG. 2 includean electronic circuit, battery and cutting edge contained in a singleenclosure that electrostatically couples with tissue or an affixedsignal amplifier but may also be embodied as an electronic circuit,battery and cutting edge that connects directly from the common of thesurgical knife 22 through a small gauge conductive wire to a conductivepad affixed to the tissue 31 or to the open node of the tuned circuit 32to provide efficient current transfer to complete the circuit.

Advantages of some embodiments of the invention include, withoutlimitation, a surgical instrument that cuts and coagulates tissuewithout the inclusion of an attached cable, is easier to maneuver duringsurgical procedures, allows faster surgical procedures by eliminatingthe need to adjust for an attached cable and is similar to standardmetal cutting instruments. In other embodiments, a cord may be used butteachings of the present invention allow for a surgical instrument witha shorter length cable, or a smaller diameter cable that is more easilymaneuvered.

FIG. 5 shows certain details of the circuitry illustrated in FIG. 1. Inthis embodiment, a cordless electronic surgical knife has a first switch50 for a coagulation mode of operation and a second switch 51 for acutting mode operation. The second switch 51 instructs a microprocessor(μP) 52 to output a continuous wave carrier for the duration of itsclosure while the first switch 50 instructs the microprocessor 52 tooutput a continuous wave carrier that is varied in pulse width or dutycycle or alternatively varies the periodicity of a continuous wavecarrier using on-off keying to create short burst of the carrier waveoutput signal. “On-Off Keying” is defined as periodically enabling ordisabling the waveform. This is primarily used in the coagulation modeto reduce the effective power by turning the wave on and off at thedesired duty cycle.

Pulse-width or duty cycle modulation may be suitable for low frequencyoperation while on-off keyed frequency pulses are typically suited forhigher frequency operation. Other switches may be included to controladditional modes of operation.

The microprocessor 52 controls the output carrier frequency of thedevice by either generating it internally, driving the input of thecarrier signal amplifier (AMP) 56 directly or (as shown in FIG. 5)creating the carrier frequency by sending a digital signal to a directdigital synthesizer (DDS) 54 which drives the carrier signal amplifier56. The output of the carrier signal amplifier 56 drives a step-uptransformer 61 to achieve the desired output voltage that is ultimatelyapplied to the cutting edge knife 62 and the “return path pickupcircuit” that includes a tuned circuit pickup elements 65, 66 and/or anantenna with tuned circuit elements 70, 69, 68, 67.

The microprocessor 52 reads inputs from an “output monitor feedbackcircuit” through an analog to digital converter (A/D) 53 that isconnected to a voltage amplifier (A) 59, which is measuring the voltageinduced across a low value resistor 60. The output of the voltageamplifier 59 is also connected to a voltage comparator 58, which if theoutput current exceeds a threshold determined by the voltage VImax,outputs a digital signal to disable the digital-to-analog output levelcontroller (D/A) 57 and is also read by the microprocessor 52. Thisprovides an adjustable mechanism to prevent current levels that maypresent discomfort to the patient and/or prevent damage to the device.

A “return monitor feedback current” is read by the microprocessor 52through a circuit made of a low value resistance 64 connected to avoltage amplifier (A) 63, which is connected to an analog-to-digitalconverter (A/D) 55. The output current and return current values areused by the microprocessor 52 to adjust the output voltage presented tothe cutting edge 62 by adjusting the voltage presented to the voltagecontrolled amplifier 56 fed by a digital-to-analog voltage converter 57.In surgical applications, the voltage presented to the cutting edge 62should be sufficient to maintain an appropriate current through thetissue for cutting or coagulation.

As tissue impedance may vary or the feedback path coupling may vary, theoutput voltage is varied to maintain the desired current through thetissue. The return path for the cutting and coagulation current isaccomplished by using a variety of methods to enhance power transferefficiency. A tuned circuit intended for RF electromagnetic coupling infrequencies ranging from VLF to UHF includes a tuned capacitor 65 (whichmay be a digitally tuned capacitor) and a pickup inductor 66 to capturethe return path signal. This signal is fed to the current sense resistor64 which in turn is coupled to the output of the step-up transformer 61.In addition, a metal plate (not shown) may be attached to the open sideof the tuned circuit including the tuned capacitor 65 and the pickupinductor 66 to provide an additional capacitive coupled return path.

The microprocessor 52 adjusts the frequency of the tuned circuit byadjusting the digitally tuned capacitor 65 to a value appropriate forthe selected operating frequency. For frequencies in the GHz range, anantenna 70 provides a return path and is connected to a unity-gainbroadband amplifier (A) 69 that feeds a tuned circuit comprising of atuned capacitor 67 (which may be a digitally tuned capacitor) and aninductor 68. The unit-gain broadband amplifier 69 may be eliminated inother embodiments of the device to provide a straight return path to thetuned circuit including the tuned capacitor 67 and inductor 68.

In an alternative mode of operation shown in FIG. 5, this embodiment ofthe present invention is capable of detecting an optimum operatingfrequency among several selectable bands, which may be selected by theuser with an additional switch coupled to the microprocessor 52.Different tissues in the body such as liver, fat, muscle, etc., areknown to have different resonant frequencies. However, resonantfrequencies of a specific tissue type can vary from patient to patient.This embodiment of the present invention can determine the resonantfrequency of a specific tissue of a specific patient by injecting avariable frequency to the carrier signal amplifier 56 and monitor for asignal peak from the return path analog-to-digital converter 55. Theoptimum operating frequency may also be determined by injectingbroadband noise into the carrier signal amplifier 56, and applying aFast Fourier Transform (FFT) on the input data of the return pathanalog-to-digital converter 59 to determine a peak or resonant frequencyof the tissue. The FFT algorithm is similar or equivalent to commonspectrum analyzer algorithms that provide amplitude versus frequencyplots across a particular frequency range. Once a resonant frequency isdetermined for a desired tissue to be cut or cauterized, the function ofthe device can be impeded once the blade is no longer in contact withthat type of tissue. In alternative embodiments, if a resonant frequencyof a non-desired tissue type is determined, the function of the blademay be limited to all tissue except the non-desired type. For example,if a procedure is desired for tissue surrounding a bone, the function ofthe blade may be limited to all operating frequencies that arenon-resonant to the bone. Once contact is made with bone tissue, theoperation of the blade stops in order to limit damage to the bone.

The embodiment of the present invention in FIG. 6 shows methods forelectromagnetic coupling between a surgical knife 80 and a transmittingantenna or inductor 82 enclosed in the signal amplifier 24 device (shownin FIG. 2) that may be attached to the tissue of the patient. The signalamplifier 24 may either actively amplify the signal or the signal may beradiated passively without additional amplification. Proper alignment ofthe polarization of the receiving antenna or inductor of the surgicalknife 80 with the transmitting antenna or inductor 82 increaseselectromagnetic signal transfer 83. During use, the surgical knife 80 ismoved in varying positions providing a less than optimum return path.The surgical knife 80 can increase the voltage to make up for thissignal loss.

Another embodiment of the invention also shown in FIG. 6 includesantenna or inductors that are polarized in the x, y and z planes. Asurgical knife 84 may contain an antenna or inductor aligned in thex-plane 87, and antenna or inductor in the y-plane 86, and an antennainductor in the z-plane 85. The signal amplifier 24 device also mayinclude a transmitting antenna or inductors in the x-plane 90, they-plane 89 and z-plane 88. This reduces the voltage requirements for thesurgical knife 84 to compensate for the return path polaritymisalignment resulting from normal movement and use of the surgicalknife 84.

FIG. 7 shows another embodiment of the present invention that usesgravity to align the polarization of the receiving and transmittingantennas or inductors. A surgical knife 90 houses an element thatcontains an inductive receiving element 92 that is encapsulated in aninner enclosure such a hollow inner sphere 93. The inductive element 92is floating in a liquid material 94 which in turn is encapsulated in anouter enclosure such as an outer sphere 95. The liquid should have a lowenough viscosity to track the surgeon's knife movement during use. Theencapsulated inductive receiving element is connected by two flexibleinsulated wires. The inner sphere 93 is weighted so that polarization ofthe receiving element 92 is aligned with the earth's gravity regardlessof the position of the surgical knife 90. A signal amplifier 91, whichis attached to the surface of the patient tissue 100, houses a similarelement that contains the inductive receiving element 96 that isencapsulated in an inner enclosure such as an inner sphere 97 which isfloating in a liquid material 98 which in turn is encapsulated in anouter enclosure such as an outer sphere 99. The inner sphere 97 isweighted such that the polarization of the transmitting element 96 isaligned with the earth's gravity regardless of the position or placementof the signal amplifier 91 thereby ensuring alignment between thereceiver element 92 and transmitting element 96 and provides an optimumreturn path for the device.

FIG. 8 shows another embodiment of the present invention with a signalamplifier used for varying cutting frequencies. In this embodiment, thesignal amplifier used for varying cutting frequencies is affixed to thetissue of the patient through a conductive pad 115 that includes anantenna 110 and a transceiver (XCVR) 111 that receives operatingfrequency commands from the surgical knife. The commands ensure that thesignal amplifier is tuned to the same frequency as the surgical knife tofacilitate maximum power transfer. The frequency change command signalsent from the surgical knife is received by the antenna 100 anddemodulated by the transceiver 111. The demodulated signal is read by amicroprocessor 112 which sends a signal to the variably tuned capacitor113 that changes the resonant frequency of the tuned circuit with theinductor 114. The signal is transferred from a conductive pad 115affixed to the patient. The microprocessor 112 sends an acknowledgementcommand to the transceiver 111 which transmits the signal to the antenna110 which is detected and decoded by the surgical knife.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed here. Theforegoing description is therefore considered in all respects to beillustrative and not restrictive. Therefore, the present inventionshould be defined with reference to the claims and their equivalents,and the spirit and scope of the claims should not be limited to thedescription of the preferred embodiments contained herein.

What is claimed is:
 1. A surgical apparatus, comprising: a blade with anedge for contacting tissue of a patient; a differential amplifiercircuit configured to provide a signal having a voltage and a current tothe blade at a certain frequency and waveform; an output monitorfeedback circuit that monitors frequency and amplitude data from thedifferential amplifier circuit; a return monitor feedback circuit thatmonitors that monitors frequency and amplitude data from the tissue; anda microprocessor that receives the frequency and amplitude data from theoutput monitor and from the return monitor and adjusts at least one ofthe voltage, frequency and waveform provided by the differentialamplifier.
 2. The apparatus of claim 1, where the microprocessor setsthe differential amplifier to provide a signal having an initialvoltage, frequency, and waveform.
 3. The apparatus of claim 2, where theinitial voltage, frequency, and waveform is set to operate the blade ina coagulation mode.
 4. The apparatus of claim 2, where the initialvoltage, frequency, and waveform is set to operate the blade in acutting mode.
 5. The apparatus of claim 1, where the microprocessoradjusts the voltage, frequency and waveform provided by the differentialamplifier through a waveform shaping circuit.
 6. The apparatus of claim1, where output monitor feedback circuit adjusts the voltage, frequencyand waveform provided by the differential amplifier through a waveformshaping circuit.
 7. The apparatus of claim 1, where the microprocessordetermines a type of tissue in contact with the blade from data receivedfrom the return monitor feedback circuit.
 8. The apparatus of claim 7,where the microprocessor receives an indication of a desired tissue typeand is configured to halt operation of the apparatus if the blade is incontact with non-desired tissue type.
 9. The apparatus of claim 8, wherethe microprocessor provides a warning to a user if the blade contacts anon-desired tissue.
 10. The apparatus of claim 7, where themicroprocessor receives the indication of the desired tissue type from aselection by a user.
 11. The apparatus of claim 1, where themicroprocessor determines a type of tissue in contact with the bladebased on a resonant frequency of the tissue.
 12. The apparatus of claim11, where the resonant frequency is determined by transmitting avariable frequency signal to the tissue and finding a return signalpeak.
 13. The apparatus of claim 11, where the resonant frequency indetermined by transmitting broadband noise to the tissue and applying aFast Fourier Transform algorithm to a return signal.
 14. The apparatusof claim 1, where frequency of the signal provided by the differentialamplifier is about 400 kHz.
 15. A cordless surgical apparatus,comprising: a blade with a surface edge for contacting tissue of apatient, where the blade is operably coupled to a receiving antenna; asignal amplifier with a transmitting antenna that transmits a signal tothe receiving antenna at a certain frequency and waveform; an outputmonitor feedback circuit that monitors frequency and amplitude data froma differential amplifier circuit; a return monitor feedback circuit thatmonitors that monitors frequency and amplitude data from the tissue ofthe patient; and a microprocessor that receives the frequency andamplitude data from the output monitor and from the return monitor andadjusts the voltage, frequency and waveform provided by the differentialamplifier.
 16. The apparatus of claim 15, where the transmitting antennacomprises at least two separate inductive circuits aligned on differentplanes with respect to one another.
 17. The apparatus of claim 16, wherethe transmitting antenna comprises three inductive circuits that arerespectively aligned in the x, y and z planes.
 18. The apparatus ofclaim 15, where each of the transmitting antenna and the receivingantenna is encapsulated inside an enclosure floating in a liquidmaterial so that each antenna is aligned by gravity.